Okay, if you say that any way information gets into a car is v2i, then v2i is necessary. But I don't think that's how Junko or the commenters view v2i. I think the question these articles are asking is will we have to change the environment? Will new communication devices in cars and the infrastructure be necessary in order for self-driving cars to operate safely?

If there's traffic congestion somewhere beyond visual range of the human driver, hopefully the human driver will have heard about it in a traffic report and found an alternate route. Or on some roads you get those LED warning signs about problems ahead. If the human driver ignores these V2I options, he gets stuck in traffic.

If a human drives along a street with multiple traffic lights in a row, often the traffic lights are timed (more or less) to the speed limit signs, so you can drive at a steady speed and most of the lights will be green (only works properly on one-way streets, obviously). If the human driver ignores the speed limit signs, he will have to stop at every light.

These are all forms of V2I that a truly self driving car also needs, in addition to maps, merging lane indications, modified traffic patterns in construction zones, and all the many other examples of V2I we have already talked about.

GPS is also a form of V2I. It is conceivable eventually that GPS could be replaced by a scheme that uses actual stars instead of the GPS constellation of aritificial stars (satellites). At least, while the stars are visible. More like migratory birds. In the meantime, this navigation data too has to be provided via artificial V2I.

My point was that if that's a valid argument for self-driving cars needing v2x, then it also implies that human-driven cars need v2x. But no one is going to say that people shouldn't be driving cars if they can't see around corners or a km ahead.

"Well, unfortunately, not really. You can't see what's happening a kilometer ahead when you are driving a car."

That's right, Junko. Another of many examples, a work zone will often create different traffic patterns and different speed limits, from those a stale Google map might indicate. (The Google map itself being a form of V2I, btw.) Plus, the traffic congestions possibilities up ahead, beyond the range of car sensors, which will deteremine a different route must be taken.

A car's own sensors won't get this, UNLESS they can read road signs and pavement markings, and never mind the traffic reports. All of these are forms of V2I comms. Any time the car reads human-generated information provided by the infrastructure, that constitutes V2I comms.

And it's not enough to rely on what the cars in front of you are doing. Obviously, someone has to be the first in line, or the only car in the vicinity, so that car has to get up-to-date information.

@BarrySweezey, I think you just made a perfect argument where the U.S. automotive industry is heading to. Let's see how far "Google cars" or any other autonomous cars can get to reduce accidents -- before making too much commitment to building V2X infrastructure.

But as to what you wrote:

"V2X can give a driver more visibility when cars are turning at a corner. It also offers the driver more information about what's happening a kilometer ahead." Fine, but that's true for human drivers, too.

Well, unfortunately, not really. You can't see what's happening a kilometer ahead when you are driving a car.

That is quite right, the life is full of threats, via science and technology we are trying to cope-up with the threats and improve the possibilities of living, on the same path I am very much sure that these developments will be ultimately leading towards better road safety, but this was just a point in the discussion.

"V2X can determine the vehicle's position relative to other vehicles, intersections, and infrastructure." So can the car.

"V2X can coordinate movement and timing, particularly through dangerous intersections." Seems like you give the infrastructure more credit for smarts that you're willing to give the car. Herds, schools and flocks manage to turn on a dime without carrying transmitter-receivers.

"V2X can give a driver more visibility when cars are turning at a corner. It also offers the driver more information about what's happening a kilometer ahead." Fine, but that's true for human drivers, too.

If self-driving cars prove themselves unable to compile a safety record better that humans', then they need v2x. Otherwise, they don't. It's an empirical question.

But if they turn out to require it, they'll take a lot longer to be realized and cost a lot more, so we should try like heck to see what they can do without it.